Method of annealing sheet metal



Patented June 5, 1928".

UNITED sTAfrl-:sIA

PATENT oFF/lcE.

wILEELu REUss, or ammm, GEBMAY, AssIGNoB. ro Jon. uonnrz mm? s.-G., or

ALTENA, GERMANY, JoINT s'rocx coxramr or GERMANY.

METHOD OF ANNALING SHEET METAL.

Application :flle June fi 1926, Serial No. 118,384, andiin Germany September 85, 1985.

My invention-relates to improvements in the-method of annealing sheet metal. ln the m'anufacture of the receivers used in telephony and radio industry the diaphragms must be made from perfectly plane sheet metal which is free of tension. lVhen annealing a pile of superposed plates, as is usual fol; example in the manufacture of fne sheet metal, it isV iinpossible completely to' is no'welding of thesheet metal plates, and

which can be carried. out at low cost. lVith this object in view my invention consists in separating the piles of sheet metal strips by parallel members made from a material having a coeflcient of expansion difierent from that of'the sheet metal, and anneali'ng the piles under pressure.

In carrying out my improved method I- pack the sheet metal strips within a' rectangula'r annealing casing so that the individual plates are disposed vertically and till out the breadth of .the casing, the casing being made from a material having a coetlicient of expansion lower than that of the blanks. For e'xample, when annealing sheet metal strips made from iron having a coeflicient of expansion of about 0.000011 I use an annealing box made from an iron-nickel alloy contalning about 36% of nickel,-said alloy being known in the trade under the name of invar and having a coeflicient of expansion of about 0.00000045.v VVhen heating thesheet metal strips at annealing temperature which in case of iron is from 400 to 600 C. the expansion of the sheet metal exceeds that of the box, so that the' small interstices between the successive metal strips resulting from Vpacking the piles are removed. The platesare forced against the walls of the aunealin box. and the irregularities resulting from co d rolling are perfectly relnoved.

Preferably plane plates made from a material having a coefiiciet of expansion higher than that of the metal strips are placed at .suitable distance apart between the sheet meta-l strips, in which` case the smoothing action may be increased by applying higher pressure to Ithe pile. For example, when annealing iron strips I use copper plates having a coelficient of expansion of 0.000017.

In order that my invention be more clearly understood a pile of metal plates packed in an annealing box has been .shown in the accompanying drawing, in which Fig.' 1, is a sectioual elevation of the .pile

and box and Fig. 2, is a to plan view of Fig. v1. As appears rom the figures, the sheet metal strips b are vertically disposed within an annealing box a so as to fill out the whole breadth of the rectangular annealing box. The box a is made from a material havinga low coeflicient of expansion, such for .example as invar; Between4 the piles of sheet metal strips there are spaced plates e made from a material having a coefiicient of ex-= pansion higher than that of the strips to be annealed. The box is heated at the desired temperature say from 400 to 6009 C; within an annealing furnace, and thereafter it is slowly cooled. After removing the strips from the box the sheet metal plates are found to be prfectly plane and freeof tension.

While in describing the invention reference has been madeto sheet metal used in the manufacture oftelephoned diaphragms and the like I wish it to be understood thatmy improved method may be generally used for annealing sheet metal wherever a sheet.

metal is needed which is perfectly smooth and free of tension. For ex'ample I may use the method for` annealing sheet metal used in the manufacture of cases for photographic apparatus.

claim: i

1. The method of annealing sheet metal, which consists in subjecting a pile of parallel plates of sheet metal to a pressure which varies in proportion tothe teln erature to which the metal is subjected, by eating the plates and at the same time restraining the outer surfaces of the outermost plates equally throughout their entire area to resist the expansion in thickness of the platesduring heat treatment, whereby the gradual expansion of the material due to increase of temperature resisted by the restraining efl'ect will generate. a graduallyincreasing pressure to remove irre larities in the sheet material being annea ed. 4

2. The method of annealing sheet metal, which consists in subjectirfg a pile of paral- -lel plates of sheet metal to a pressure which while restraining the outer sur aces of thev outermost plates, whereby the combined expansion in thickness of the plates of the pile and the interspersed plates as the temperature is i'ncreased will generate a gradually increasing pressure to remove irregularities in the sheet'metal being annealed.

3. The method of annealin sheet metal, which consists in subjecting t e metal to a pressure during heat treatment which' varies in proportion to the temperature thereof, by placing a pile of parallel plates 4of the sheet metal snugly between abutments having' a coeflicient of expansion smaller than that offlthe metal, and which are substantially co-extensive. in area with the adjacent surfaces of the outer plates and then heating bein the plates, -whereby the radual expansion will generate a gradually increasing pres sure to remove irregularities in the sheet metal being annealed.

4. The method of annealin which consists in subjecting t e metal to a pressure during heat treatment which varies in proportion to the temperature thereof, by placing .a p`ile of parallel plates of the sheet metal snugly in a container having a coeflicient of expansion smaller than that of the metal, with the plates vertical to avoidthe effect of their weight, and (the outer lplates of the pile abutting the two opposite walls of the container, and the intermediate-plates in contact with each other and then heatmg the plates whereby the gradual expansion in thickness of the plates due to increase of temperature resisted by ,the abutment will generate a gradually increasing pressure to remove irregularities in the sheet metal being annealed.

In testimony whereof I hereunto aflix my Signature.

WILHELM REss.

sheet metal, 

